1. Field of the Invention
The present invention relates to a shoe adapted more particularly for sport practice, of the type constituted of an upper and an external sole, as well as of a lining at least partially elastic arranged within the upper.
2. Background and Material Information
The use of such elastic linings, especially in sport shoes, is increasingly favored for the proprioceptive qualities which they provide.
For example, the U.S. Pat. No. 2,147,197, filed in 1936, shows a sport shoe constituted of a jersey sock anchored through its end on the sole, and of an external upper partially surrounding the sock and fixed on the sole in manner that is totally independent of the sock, the knitted structure of the sock providing the latter with a certain elasticity.
The U.S. Pat. No. 4,736,531, filed more recently in 1987, shows a sport shoe, adapted more particularly to aerobics, which includes a kind of internal half-sock completely surrounding the fore-foot, and whose end is anchored on the external sole, the sock being free to "grip" the foot independently of the external upper.
In this case, the sock is made out of an extensible material such as that known by the commercial name spandex, which, unlike the U.S. Pat. No. 2,147,197, actually enables the sock to tightly envelop the foot and to follow the movements thereof.
Different constructions of sport shoes have likewise been proposed by the Applicant in the French document No. FR 2 711 896, such shoes being more particularly adapted for cross country skiing, and incorporating a lining made of an elastic material arranged within an upper, in order to increase the sensations of the foot and of the ankle, and to locate, in an accurate manner, the respective space positions of such sensations that are indispensable to obtain a good precision of the movement.
In fact, the type of shoe known from these two patents uses the proprioceptive qualities of certain parts of the foot and of the ankle.
To obtain an optimum response, it is necessary that the elastic lining tightly envelop the foot and the ankle by constituting a kind of a second skin, regardless of the foot inserted inside the shoe.
Such an elastic lining must therefore be configured so as to define, at rest, a volume slightly less than the volume of the foot which it is adapted to receive, so as to exert a slight regular pressure thereon, without any excessive tightening.
In practice, these elastic linings are therefore designed with a volume slightly less than the volume of the narrowest foot that can be placed inside the shoe.
As a result, difficulties arise when putting on the shoe, especially for larger feet, these difficulties being more substantial as the elastic lining "rises" higher on the ankle as in the case of the sport shoes featured in the French document No. 2 711 896.
It has been provided in the above-identified French document No. 2 711 896 to provide the elastic lining with a slit allowing for the positioning of the foot and being capable of being closed by self-gripping means.
However, such a construction does not allow for an accurate adjustment and adaptation of the volume of the sock or elastic lining to the volume of the foot.
Moreover, this construction with an opening slit is not compatible with the use of a high, closed upper which only provides a very limited access to the inside of the shoe, such access being insufficient to easily open and close the slit of the lining.
One can also provide that the volume of the elastic lining correspond to that of an average foot to be placed inside of the shoe. In this case, the problem of inserting large feet in the shoe remains, whereas a narrow foot does no longer benefits from the tight enveloping of the elastic lining.
Finally, it is also advisable to be able to maintain a completely closed elastic lining structure, especially for reasons related to imperviousness.